Noise pollution refers to any unpleasant, damaging or irritating noise that has the potential to harm people, wildlife or the environment. The decibel (dB) is the main unit used to measure the intensity or loudness of sounds. A sound can also be measured by its pitch, which is the frequency of sound vibrations per second.

Correct Option: A

Noise pollution refers to any unpleasant, damaging or irritating noise that has the potential to harm people, wildlife or the environment. The decibel (dB) is the main unit used to measure the intensity or loudness of sounds. A sound can also be measured by its pitch, which is the frequency of sound vibrations per second.

The freezing point of water is the temperature at which water changes phase from a liquid to a solid. Under normal conditions, ordinary water freezes at 0°C, or 32°F. The temperature may be lower if supercooling occurs or if there are impurities present in the water which could cause freezing point depression to occur.

Correct Option: D

The freezing point of water is the temperature at which water changes phase from a liquid to a solid. Under normal conditions, ordinary water freezes at 0°C, or 32°F. The temperature may be lower if supercooling occurs or if there are impurities present in the water which could cause freezing point depression to occur.

A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia and thus resist changes in rotational speed, enabling the engine to run at a constant, uniform motion. In the Industrial Revolution, James Watt contributed to the development of the flywheel in the steam engine.

Correct Option: B

A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia and thus resist changes in rotational speed, enabling the engine to run at a constant, uniform motion. In the Industrial Revolution, James Watt contributed to the development of the flywheel in the steam engine.

Transition metal ions have an incomplete set of 3d electrons. Changes in the energy of these electrons correspond to the energy of visible light. The absorption of visible light by these ions lend colour to gems.

Correct Option: D

Transition metal ions have an incomplete set of 3d electrons. Changes in the energy of these electrons correspond to the energy of visible light. The absorption of visible light by these ions lend colour to gems.

In the case of damage to human body due to radiation, the most important factor is the amount of the dose - the amount of energy actually deposited in the body. The absorbed radiation dose, the amount of energy absorbed per gram of body tissue, is usually measured in units called rads. Another unit of radation is the rem, or roentgen equivalent in man. For practical purposes, 1 rad (absorbed dose) = 1 rem or 1000 mrem (dose equivalent) (Source: United States Nuclear Regulatory Commission).

Correct Option: A

In the case of damage to human body due to radiation, the most important factor is the amount of the dose - the amount of energy actually deposited in the body. The absorbed radiation dose, the amount of energy absorbed per gram of body tissue, is usually measured in units called rads. Another unit of radation is the rem, or roentgen equivalent in man. For practical purposes, 1 rad (absorbed dose) = 1 rem or 1000 mrem (dose equivalent) (Source: United States Nuclear Regulatory Commission).